Methods and systems for communicating signaling system 7 (SS7) user part messages among SS7 signaling points (SPs) and internet protocol (IP) nodes using signal transfer points (STPs)

ABSTRACT

Methods and systems for transmitting user part messages between signaling system seven (SS7) signaling points over an internet protocol (IP) network include receiving, at a signal transfer point, a first SS7 user part message. The first SS7 user part message can be received from a first SS7 signaling point, such as a service switching point (SSP). The first SS7 signaling point is encapsulated in a first IP packet. The first IP packet is transmitted to a second SS7 signaling point over an IP network.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.09/443,712, filed Nov. 19, 1999, which is a continuation-in-part of U.S.patent application Ser. No. 09/205,809 filed Dec. 4, 1998 (U.S. Pat. No.6,324,183), and which claims the benefit of U.S. Provisional PatentApplication No. 60/127,889 filed Apr. 5, 1999, and U.S. ProvisionalPatent Application No. 60/137,988 filed Jun. 7, 1999, the disclosure ofeach of which are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates generally to methods and systems forcommunicating signaling system 7 (SS7) user part messages among SS7nodes and internet protocol (IP) nodes. More particularly, the presentinvention relates to methods and systems for communicating SS7 user partmessages among SS7 signaling points and IP nodes using signal transferpoints (STPs).

BACKGROUND ART

Modern telecommunications networks generally include two separatecommunication pathways or subnetworks. The first is a voice network thathandles the transmission of voice or other information between users.The second is a signaling network that facilitates the dynamic linkingof a plurality of voice network circuits, such that a voice-typeconnection is established between a calling party and a called party.These functions are generically referred to as call setup and call teardown. Additionally, the signaling network provides a framework throughwhich non-voice related information can be transported in a manner thatis transparent to the user. This signaling technique is often referredto as “out of band” signaling, where the term “band” implies voice band.Common examples of such out of band data transport are the access of 800number database services, calling card verification services, numberportability services, and caller ID services.

In order to provide consistent and reliable communication across thesignaling network infrastructure, a common or standard digital signalingprotocol known as SS7 has been developed. SS7 is an out of band commonchannel signaling system that uses labeled messages to transport circuitrelated signaling information, non-circuit related signalinginformation, network resident database service information and otherinformation that can be used for the establishment of communicationservices.

From a hardware perspective, an SS7 network includes a plurality of SS7nodes, generically referred to as signaling points (SPs), that areinterconnected using signaling links, also referred to as SS7 links. Atleast three types of SPs are provided in an SS7 network: serviceswitching points (SSPs), signal transfer points (STPs), and servicecontrol points (SCPs).

An SSP is normally installed in tandem or Class 5 offices. The SSP iscapable of handling both in-band signaling and SS7 signaling. An SSP canbe a customer switch, an end-office, an access tandem and/or a tandem.An STP transfers signaling messages from one signaling link to another.STPs are packet switches and are generally installed in mated pairs.Finally, SCPs control access to databases, such as 800 numbertranslation databases, 800 number carrier identification databases,credit card verification databases, etc.

Signaling datalinks are transmission facilities used to connect SPstogether. They are dedicated bidirectional facilities operating at 56kbps in the U.S. and Canada and at 64 kbps when clear channel capabilityis deployed. Normally, every link has a mate for redundancy and enhancednetwork integrity.

Signaling datalinks include access links or “A” links that connect SSPsto STPs and that connect SCPs to STPs, as shown in FIG. 1. Bridge linksor “B” links are used to connect mated STPs to other mated STPs that areat the same hierarchical level, as shown in FIG. 2. Cross links or “C”links connect mated STPs together, as shown in FIG. 3. C links are usedfor passing messages between STPs when signaling network failures areencountered.

Diagonal links or “D” links connect STPs of different hierarchicallevels, as shown in FIG. 4. Extended links or “E” links connect SSPs toSTPs that are not within their associated local STP area, as shown inFIG. 5. Finally, fully associated links or “F” links connect SSPsdirectly together without STPs, as shown in FIG. 6. FIG. 7 is a blockdiagram of a two-level SS7 network including a summary of possible linkdeployment.

SS7 also includes a network protocol. As a protocol, SS7 defines ahierarchy or structure of the information contained in a message or datapacket that is transmitted between SPs of an SS7 network over signalinglinks. This internal data structure is often referred to as an SS7protocol stack which includes the following four SS7 levels:

-   -   Level 1: The Physical Level    -   Level 2: The Datalink (or Link) Level    -   Level 3: The Network Level    -   Level 4: User Parts and Application Parts Level

The physical level, also referred to as message transfer part (MTP)level 1, is the lowest or most fundamental level and is the first levelthat is used to interpret and process an incoming message. This leveldetermines and/or provides the electrical characteristics to transmitthe digital data over the interface being used. Followinginterpretation/processing at the physical level, the incoming message ispassed up the stack to the datalink level.

The datalink level, also referred to as MTP level 2, resides adjacentand above the physical level and is responsible for providing errordetection/correction and properly sequenced delivery of SS7 messagepackets. Following interpretation/processing at the datalink level, theincoming message is passed up the stack to the network level.

The network level, also referred to as MTP level 3, resides adjacent andabove the datalink level and provides the information necessary formessage packet routing, message packet discrimination, and messagepacket distribution. Functionally, message discrimination determineswhether the message packet is addressed to the receiving SP or toanother SP. If the message contains the local address of the receivingSP, then the message is passed on to message distribution. Messagedistribution routes the message to the proper application part or userpart within the receiving SP. If the message is not addressed to thereceiving SP, then it is passed on to the message router, whichdetermines the physical address of the SP to which the message is to besent. Following interpretation/processing at the network level, theincoming message is passed up the stack to the user parts andapplication parts level.

The user parts and application parts level resides adjacent and abovethe network level. User part protocols perform call setup and tear down.Exemplary user part protocols that can be included in SS7 level 4 areISDN user part (ISUP), telephone user part (TUP), and broadband ISDNuser part (BISUP).

Application part protocols provide access to network databases forservices, such as 800 number service, credit card verification, andnumber portability. The transaction capabilities application part (TCAP)protocol is an example of an SS7 level 4 protocol that can be used toprovide access to these and other services.

The above description has assumed that an incoming message is beingprocessed. An outgoing message is passed through the protocol stack inthe opposite direction, entering at the user part level and exiting fromthe physical level. FIG. 8 illustrates SS7 protocol architecturerelative to SS7 levels and relative to standard Open System Integration(OSI) layers.

The above-mentioned SS7 protocol levels are implemented by hardware andsoftware residing in SS7 signaling points, such as signal transferpoints (STPs). A high performance STP is marketed by the assignee of thepresent application as the Eagle® STP. A block diagram of a conventionalEagle® STP is shown in FIG. 9. A detailed description of the Eagle® STPcan be found in the Eagle® Feature Guide PN/9110-1225-01, Rev. B,January 1998, published by Tekelec, the disclosure of which is herebyincorporated herein by reference. As described in this publication,Eagle® STP generally designated 900 includes the following subsystems:maintenance and administration subsystem (MAS) 910, communicationsubsystem 920 and application subsystem 930. MAS 910 providesmaintenance communications, initial program load, peripheral services,alarm processing and system disks. Communication subsystem 920 includesan interprocessor message transport (IMT) bus that is the maincommunication bus among all subsystems in Eagle® STP 900. This highspeed communications system functions as two 125 Mbps counter-rotatingserial buses.

Application subsystem 930 includes application cards that are capable ofcommunicating with the other cards through the IMT buses. Theillustrated application subsystem 930 includes three types ofapplication cards: link interface module (LIM) 940 that provides SS7links and X.25 links, application communication module (ACM) 950 thatprovides a TCP/IP interface for sending copies of SS7 message signalunits (MSUs) over ethernet, and application service module (ASM) 960that provides global title translation, gateway screening and otherservices. A translation service module (TSM) can also be provided forlocal number portability.

LIM 940 provides level 1 and some level 2 functions on SS7 signalinglinks. ACM 950 provides access to a remote host for an STP LAN feature.The STP LAN feature provides unidirectional access to copies of SS7 MSUsfrom the STP to a remote host. Unidirectional connection from the STP toa host is provided through an ethernet LAN using TCP/IP protocol.Finally, ASM 960 provides additional memory that is used to storetranslation tables and screening data. A detailed description of theEagle® STP is provided in the above-cited Feature Guide and need not befurther described.

A brief conceptual overview of the Eagle® STP is provided in thebrochure entitled Eagle® STP Platform, Publication 908-0126-01, Rev. A,Tekelec, 1997. As described therein, the Eagle® STP is a high capacity,fully fault tolerant packet switch and self-contained local area networkfor exchanging data messages between a half-dozen to several hundred ormore message processing modules. In the Eagle® STP system architecture,three functionally specific application subsystems access each other viaa communications subsystem which includes dual counter-rotating, 125Mbps IMT buses. The application subsystems include LIMs that provide SS7and X.25 access to telecommunication signaling networks, ACMs thatprovide TCP/IP access to local area networks and a MAS that providesmaintenance communication, peripheral services alarm processing andsystem disks. As stated in this brochure, “ACMs communicate directlywith external, collocated service application systems via a TCP/IP, 10Mbit/sec LAN interface mounted on the Ethernet Interface Appliqué (EIA).Examples of external application systems include: an SCP not equippedwith SS7 signaling links, a routing or charging database system,cellular/PCS home or visitor location registers (HLR, VLR), a messageaccounting system, a voice/record/image processing system, and otherintelligent network (IN) service nodes and peripherals that requiredirect interface via SS7 signaling links.” Thus, the Eagle® STP platformpublication does not describe communication between an STP and an SS7node. The ACM card described therein is used primarily for diagnosticpurposes.

A detailed description of the operation of the Eagle® STP-LAN interfacefeature is provided in the brochure entitled Eagle® STP STP LANInterface Feature, Publication 908-0134-01, Rev. B, Tekelec 1997. Asdescribed therein, “The STP-LAN Interface Feature enables the collectionof copies of SS7 messages that transit the Eagle® STP. This feature,along with user-provided data processing equipment, allows the Eagle®STP to perform functions beyond normal Signal Transfer Point (STP)functionality, such as auditing and accounting functions, message trapand trace and protocol conformance analysis. The Eagle® STP-LANInterface Feature enables the user to connect external data collectionor processing systems directly to the Eagle® STP via TCP/IP, 10Mbits/sec Ethernet LAN. It enables a user to select either ISUPmessages, SCCP/TCAP messages, or both, for transfer to the externalmonitoring system. It also adds a time-stamp to identify the selectedmessages and their sequence for subsequent processing.” As is also shownin this brochure, the Ethernet LAN link is a unidirectional link fromthe ACM to an external processor (host) for diagnostic purposes.Moreover, the Eagle® STP LAN feature is not suitable for communicatingSS7 messages between SS7 signaling points, not to mention communicatingmessages to SS7 signaling points for call setup or other call-relatedsignaling functions.

While communicating SS7 messages over SS7 links can be desirable in someinstances, it can also be desirable to communicate SS7 messages overother types of networks. SS7 links provide a high-bandwidth, reliablecommunication medium for SS7 messages. However, a dedicated SS7 link isexpensive and often provides too much bandwidth for a given application.In addition, the proliferation of networks other than SS7 networks makesthese networks possible candidates for SS7 message traffic. One type ofnetwork conventionally used to transport SS7 messages is an X.25network. For example, it is known to provide a database transport accessfeature that intercepts SS7 message signaling units originating from anX.25 network. This feature is described in a brochure entitled Eagle®STP Database Transport Access Feature, Publication 908-0136-01, Rev. B,Tekelec, 1997.

It is also known to use protocol converters for some protocols inconnection with STPs. For example, the Eagle® STP X.25 protocolconversion feature provides interfacing and connectivity between nodeson an SS7 network and nodes on an X.25 network. This feature isdescribed in a brochure entitled Eagle® STP X.25 to SS7-IS.41 ProtocolConversion Feature, Publication 908-0135-01, Rev. B, Tekelec, 1997.Similarly, it is known to provide an ANSI-ITU gateway to enable anEagle® STP to interconnect to other types of signaling networks. Thisfeature is described in a brochure entitled Eagle® STP ANSI-ITU GatewayFeature, Publication 908-0133-01, Rev. B, Tekelec, 1997.

Protocol converters are also known for translating protocols between SS7and non-SS7 networks. For example, the Tekelec SS7-Frame Relay AccessDevice (FRAD) translates SS7 protocol information between an SS7 networkand a frame relay network. This feature is described in a brochureentitled SS7-Frame Relay Access Device SS7 Protocol InformationTranslator, Publication 908-0167-01, Rev. A, Tekelec, 1997.

Protocol conversion for SS7 networks is also described in U.S. Pat. No.5,793,771 to Darland et al., entitled “Communication Gateway”(hereinafter, “the '771 patent”). The '771 patent describes a system andmethod for protocol translation between a foreign postal telephone andtelegraph network and a domestic communication service provider, forverifying international credit card numbers. The system includes acommunications gateway that consists of a computer located between theforeign network and the domestic network exclusively for performingprotocol conversion. The communications gateway is not a signal transferpoint. The communications gateway is only a protocol converter, and thecommunications gateway includes an SS7 module for sending and receivinga plurality of incoming and outgoing SS7 queries and responses. Thecommunications gateway also includes an inbound subsystem module,coupled to the SS7 module, for translating the incoming SS7 queries froman SS7 protocol to a non-SS7 protocol.

The '771 patent discloses that the inbound subsystem module convertsincoming SS7 messages into network information distributed service(NIDS) format and TCP format. However, the only type of SS7 messagesthat are discussed are TCAP messages, where MTP and SCCP layers areremoved from the messages and a TCP header is added to the messages. Thetranslated incoming queries are forwarded to an end user using thenon-SS7 protocol. The inbound subsystem module also translates anyresponses corresponding to the incoming SS7 queries from the non-SS7protocol to the SS7 protocol.

The communications gateway of the '771 patent further includes anoutbound subsystem module, coupled to the SS7 module, for translatingoutgoing SS7 queries from the non-SS7 protocol to the SS7 protocol.Again, these queries are disclosed as being TCAP queries forinternational credit card verification. The translated outgoing queriesare sent via the SS7 module across an SS7 network. The outboundsubsystem module also translates SS7 responses corresponding to theoutgoing SS7 queries from the SS7 protocol to the non-SS7 protocol. Thetranslated responses corresponding to the outgoing SS7 queries areforwarded to an end user while in the non-SS7 protocol.

U.S. Pat. No. 5,706,286 to Reiman et al., entitled “SS7 Gateway”discloses a protocol converter separate from an STP that converts TCAPqueries to NIDS format and vice-versa for credit card validation.

U.S. Pat. No. 5,640,446 to Everett et al., entitled “System and Methodof Validating Special Service Calls Having Different SignalingProtocols” discloses a protocol converter external to an STP thatconverts TCAP queries to NIDS format for calling card transactions.

One problem with conventional protocol converters is that these devicesrequire specialized processing hardware and software that reside in aseparate location from the STP. These protocol converters also lack theprocessing speed and functionality of a signal transfer point, such asthe above-mentioned Eagle® STP.

Yet another problem with conventional protocol converters is that theprotocol converters are incapable of converting SS7 messages to otherprotocols without terminating the layer being transported. As a result,protocol converters can be required to implement the entire protocolstack.

Yet another problem with the above-mentioned protocol converters is thatthey only address translation between SS7 TCAP messages and TCP packets.In encapsulating TCAP messages, the MTP layer 3 information is strippedfrom the message. There are numerous other SS7 message payload types(ISUP, TUP, BISUP, etc.) that cannot be TCP/IP-encapsulated and routedthrough an IP network without including at least some of the routinglabel information contained in MTP level 3. The functionality of suchSS7 messages is impaired, if not destroyed in many cases without thisMTP lower level or routing label information. In practice, such aprotocol conversion task presents a more difficult and challengingproblem than the relatively simple case of TCP/IP-encapsulated TCAP/SCCPinformation.

Accordingly, there exists a long-felt need for methods and systems fortransmitting SS7 user part messages including lower-level MTP protocolinformation, over an IP network using signal transfer points.

DISCLOSURE OF THE INVENTION

The present invention includes methods and systems for communicatinguser part messages between SS7 signaling points. As used herein, thephrase “user part messages” includes any SS7 user part messages, such asISUP messages, BISUP messages, and TUP messages. In addition, the phrase“user part messages” is intended to encompass any future protocolmessages used to transport call signaling information between SS7signaling points and/or IP nodes.

According to one aspect, the present invention includes methods andsystems for transmitting SS7 user part messages between SS7 signalingpoints. A first SS7 user part message is received at a signal transferpoint from a first SS7 signaling point. For example, the first SS7 userpart message can be an ISUP message received from an SSP. The signaltransfer point encapsulates the first SS7 user part message in a firstIP packet. The signal transfer point then transmits the first IP packetto a second SS7 signaling point over an IP network.

According to another aspect, the present invention includes methods andsystems for encapsulating SS7 user part messages for transmission overan internet protocol network. In order to encapsulate the SS7 user partmessage, a signal transfer point extracts at least some of the SS7 layer3 information from an SS7 message signaling unit (MSU). The extractedportion includes SS7 routing information for the MSU. The extractedportion of the SS7 MSU is encapsulated in a transport adapter layerinterface packet including an application-level sequence number. An IPheader is added to the transport adapter layer interface packet toproduce an IP packet.

According to another aspect, the present invention includes a method fordecapsulating an IP-encapsulated SS7 user part message utilizing asignal transfer point and receives an IP-encapsulated SS7 user partmessage and removes the IP header from the message. The signal transferpoint then reads MTP layer 3 information from a data portion of themessage to determine an SS7 signaling link on which to route themessage. The signal transfer point then adds SS7 layers 1 and 2information to the message thereby forming a complete SS7 MSU.

According to another aspect, the present invention includes a method forreliably recovering SS7 user part message packets when a TCP socketfails. The method includes establishing first and second TCP connectionsover first and second sockets between first and second SS7 nodes. Datapackets are transmitted from the first SS7 node to the second SS7 nodeover one of the TCP connections. The data packets each include anapplication-level sequence number indicator for sequencing data packetsreceived by the first and second SS7 nodes. In response to determiningthat one of the TCP sockets has failed, a recovery packet is transmittedfrom each node to the other node including the application-levelsequence number indicating the last data packet received by each node.Data communications can then occur over the socket that did not fail.

According to another aspect, the present invention includes a datastructure for communicating SS7 user part messages between SS7 nodes.The data structure includes a data field for encapsulating MTP layer 3information. An application-level user part field stores anapplication-level sequence number. An IP header field stores IPinformation including an internet protocol address.

According to another aspect, the present invention includes computerprogram products comprising computer-executable media for performingsteps for processing IP-encapsulated SS7 MSUs and for encapsulating SS7MSUs in IP packets. As used herein, the phrase, “computer-readablemedium” includes: magnetic, optical, and electrical storage media, suchas disk storage devices, memory chips, and propagated electricalsignals.

It is therefore an object of the present invention to provide novel,improved methods and systems for communicating user part messagesbetween SS7 nodes using STPs.

It is another object of the present invention to provide improvedmethods and systems for communicating SS7 messages, including level 3routing information, between an STP and other SPs of an SS7 network.

It is yet another object of the present invention to provide improvedmethods and systems for communicating SS7 messages between an STP andother SPs of an SS7 network, which can reduce the capital andmaintenance expenses of connecting an STP to other SPs of an SS7network.

It is yet another object of the invention to provide methods and systemsfor communicating user part messages between SS7 nodes with increasedreliability.

These and other objects are achieved in whole or in part by the presentinvention. Some of the objects of the invention having been statedhereinabove, other objects will become evident as the descriptionproceeds, when taken in connection with the accompanying drawings asbest described hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained with reference to theaccompanying drawings of which:

FIGS. 1-7 are block diagrams illustrating signaling datalinks and SPs ofconventional SS7 networks;

FIG. 8 is a block diagram illustrating SS7 protocol architecturerelative to SS7 levels and relative to standard open system integration(OSI) layers;

FIG. 9 is a block diagram of a conventional Eagle® STP;

FIGS. 10-14 are block diagrams illustrating exemplary networkconfigurations for bidirectional communication of SS7 user part messagesbetween an STP and at least one of the other SPs in an SS7 network usingTCP/IP according to embodiments of the present invention;

FIG. 15 is a block diagram of an SP according to an embodiment of thepresent invention;

FIG. 16 is a block diagram illustrating bidirectional transport of userpart messages among SS7 and IP network elements using an STP accordingto an embodiment of the present invention;

FIG. 17 is a block diagram illustrating an exemplary networkconfiguration for user part message flow according to an embodiment ofthe present invention;

FIG. 18 is a call flow diagram illustrating exemplary user part messageflow in the network configuration illustrated in FIG. 17;

FIGS. 19 and 20 are flowcharts illustrating bidirectional communicationof SS7 messages between an STP and at least one other SP according toembodiments of the present invention;

FIG. 21 is a block diagram of exemplary hardware of an STP capable ofcommunicating user part messages over IP networks according to anembodiment of the present invention;

FIG. 22 is a detailed block diagram illustrating exemplary software inan STP for bidirectional SS7 user part message communication over SS7and IP networks according to an embodiment of the present invention;

FIG. 23 is a block diagram illustrating exemplary hardware for SS7 to IPmessage flow according to an embodiment of the present invention;

FIG. 24 is a block diagram of an exemplary data structure fortransmitting SS7 user part messages over IP networks according to anembodiment of the present invention;

FIG. 25 is a block diagram of another exemplary data structure fortransmitting SS7 user part messages over IP networks according to anembodiment of the present invention; and

FIG. 26 is a flow chart illustrating an exemplary SS7 message recoveryroutine according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the invention are shown. This invention can, however, be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the invention to those skilled in the art. Likenumbers refer to like elements throughout.

Exemplary Network Configurations for Bi-Directional Communication ofUser Part Messages

FIGS. 10-14 are block diagrams illustrating exemplary networkconfigurations for bidirectional communication of SS7 user part messagesbetween an STP and at least one of the other SPs in an SS7 network usingTCP/IP according to embodiments of the present invention. Morespecifically, FIG. 10 illustrates an exemplary network configuration forbidirectional communication of SS7 user part messages between an STP andat least one SSP using TCP/IP, to thereby replace SS7 A links withTCP/IP links. For example, STPs 1000 and 1002 can transmit SS7 user partmessages to and receive SS7 user part messages from SSPs 1004 and 1006over TCP/IP network 1008.

FIG. 11 illustrates an exemplary network configuration for bidirectionalcommunication of SS7 user part messages between STPs of the samehierarchical level, replacing SS7 B links with TCP/IP links. Forexample, mated STPs 1100 and 1102 can send SS7 user part messages to andreceive SS7 user part messages from mated STPs 1104 and 1106 throughTCP/IP network 1108.

FIG. 12 illustrates an exemplary network configuration for bidirectionalcommunication of user part messages between mated STPs using TCP/IP,replacing SS7 C links with TCP/IP links. For example, STP 1200 can sendSS7 user part messages to and receive SS7 user part messages from STP1202 through TCP/IP network 1204. Similarly, STP 1206 can send SS7 userpart messages to STP 1208 and receive SS7 user part messages from STP1208 through TCP/IP network 1204.

FIG. 13 illustrates an exemplary network configuration for bidirectionalcommunication of user part messages between STPs of differenthierarchical levels using TCP/IP links, replacing D links with TCP/IPlinks. For example, local STPs 1300-1306 can send SS7 user part messagesto regional STPs 1308 and 1310 and receive SS7 user part messages fromregional STPs 1308 and 1310 through TCP/IP network 1312.

FIG. 14 illustrates an exemplary network configuration for bidirectionalcommunication of SS7 user part messages between STPs and SSPs that arenot within the same local STP area using TCP/IP, replacing E links withTCP/IP links. For example, STPs 1400 and 1402 can be located in adifferent local area from STPs 1404 and 1406 and SSP 1408. Communicationof user part messages between STPs 1400 and 1402 and SSP 1408 would thusconventionally occur over E links. However, according to the presentinvention, the E links are replaced by TCP/IP network 1410. As such,STPs 1400 and 1402 are capable of sending SS7 user part messages to andreceiving SS7 user part messages from STPs 1404 and 1406 and SSP 1408through TCP/IP network 1410. TCP/IP can also be used to replacecombinations of A through E links by combining one or more of FIGS.10-14.

STP Including SS7/IP User Part Communicator

FIG. 15 is a block diagram of an SP generally designated 1500 accordingto the present invention. SP 1500 can also be referred to as a “node” ofan SS7 network. SP 1500 can comprise any suitable combination ofhardware and software for performing the SS7 and IP switching functions.As shown in FIG. 15, SP 1500 includes STP 1510 that transfers messagesbetween other SPs of the SS7 network using the SS7 protocol. SP 1500also includes an SS7/IP user part message communicator 1520 that ispreferably integrated within STP 1510 to bidirectionally communicate atleast some of the transferred SS7 user part messages between the STP1510 and at least one of the other SPs, such as SP 1540, of the SS7network using an IP network and preferably using TCP/IP network 1530. Inan alternative embodiment, SS7/IP user part message communicator 1520can be located external to STP 1510.

STP 1510 including SS7/IP user part message communicator 1520 can beused to provide seamless transport among SS7 user part network elements,and among IP network elements. For example, as shown in FIG. 16, STP1510 can be used to bidirectionally communicate SS7 messages and othermessages between a first signaling point SP1 and a second signalingpoint SP2 of two separate SS7 networks as shown by the bidirectionalarrow A1. Moreover, STP 1510 can also be used to bidirectionallycommunicate SS7 user part messages or other messages between a first IPnode N1 and a second IP node N2 via one or more IP networks, as shown bybidirectional arrow A2.

Finally, as shown by bidirectional arrows A3 and A4, STP 1510 can beused to communicate SS7 user part messages or other messages betweensignaling points SP1 and SP2 and IP nodes N1 and N2. Thus, an STPincluding an SS7/IP user part message communicator can become a routerfor communicating user part messages among SPs in an SS7 network,between SPs in an SS7 network and nodes in an IP network, and amongnodes in an IP network. Seamless transport of user part messages betweenSS7 and IP network elements can thereby be provided using an STP with anSS7/IP user part message communicator.

As stated above, user part messages, such as ISUP messages, are used toperform call setup and tear down functions. FIG. 17 illustrates anexemplary network configuration for communicating user part messagesbetween end offices in performing call setup. In FIG. 17, SSP 1700 isconnected to STP 1510 through SS7 link 1720. For example, SS7 link 1720can comprise an A link. STP 1510 is connected to another SSP 1730through a TCP/IP network 1740. TCP/IP network 1740 replaces an SS7 Alink between STP 1710 and SSP 1730. STP 1510 includes an SS7/IP userpart message communicator 1520 for bidirectionally communicating userpart messages between SSP 1700 and SSP 1730. In the illustrated network,the SSP 1730 is preferably capable of communicating using TCP/IP. In analternative network configuration, SSP 1730 might not be TCP/IP-enabledand an additional STP including an SS7/IP user part message communicatoror a protocol converter can be connected between TCP/IP network 1740 andSSP 1730. Either configuration is within the scope of the presentinvention.

Each of the nodes in the network configuration illustrated in FIG. 17has MTP level 3 routing information including a point code. In theillustrated network, SSP 1700 has a point code of 100.100.101. The SSP1730 has a point code of 200.200.201. STP 1510 has a point code of300.300.301. Because STP 1510 and the 1730 are connected over an IPnetwork, STP 1510 and SSP 1730 also have IP addresses. In theillustrated embodiment, STP 1710 has an IP address of 128.10.2.30 andSSP 1730 has an IP address of 128.10.2.31.

FIG. 18 illustrates an exemplary call flow diagram illustrating the flowof ISUP messages between SSP 1700 and SSP 1730 in performing call setup.In line 1 of the call flow diagram, SSP 1700 transmits an initialaddress message (IAM) message addressed to SSP 1730 to STP 1510. The IAMmessage has an originating point code of 100.100.101 and a destinationpoint code of 200.200.201. When STP 1510 receives the IAM message, STP1510 does not change the SS7 originating point code or destination pointcode. Rather, STP 1510 encapsulates the IAM message in a TCP/IP packetwith a destination IP address of 128.10.2.31, i.e., the IP address ofSSP 1730. The TCP/IP packet also includes the source IP address of128.10.2.30, i.e., the IP address of STP 1510.

In line 2 of the call flow diagram, SSP 1730 transmits an addresscomplete message (ACM) to SSP 1510. The address complete messageincludes an originating point code of 200.200.201, i.e., the point codeof SSP 1730, and a destination point code of 100.100.101, i.e., thepoint code of SSP 1700. The destination IP address, however, is that ofSTP 1510, i.e., 128.10.2.30. The STP 1510 receives the ACM message,removes the TCP/IP header, attaches any needed SS7 information, andforwards the ACM message to SSP 1700.

In line 3 of the call flow diagram, when the calling party answers thecall, SSP 1730 transmits an answer message (ANM) to SSP 1700. The answermessage can be transmitted in a manner similar to the ACM message andthus the transmission need not be further described.

Once the answer message has been received by SSP 1700, a call betweenend users 1750 and 1760 is in progress. The call continues until eitherparty goes on-hook. In the illustrated call flow diagram, when end user1760 connected to SSP 1730 goes on-hook, a release message (REL) istransmitted from SSP 1730 to SSP 1700. The release message is addressedand routed in a manner similar to the ACM message described above. TheSSP 1700 responds to the release message by transmitting a releasecomplete message (RLC) to SSP 1730. The release complete message isaddressed and routed in a manner similar to the IAM message describedabove.

Because STP 1510 performs bidirectional communication of user partmessages between end offices, the resources required for performing callsetup operations are reduced. For example, it is no longer necessary tohave dedicated SS7 links between end offices for performing callsignaling operations. One or more of the links can be replaced by an IPnetwork, such as a TCP/IP network or a UDP/IP network.

Bidirectional Communication Methods and Computer Programs

An STP for an SS7 network according to the present invention includesmeans for and provides the steps of, bidirectionally transferring SS7user part messages among SPs of the SS7 network. The STP also includesmeans for and provides the steps of bidirectionally transferring userpart messages between SPs of the SS7 network and IP nodes of an IPnetwork. The STP also includes means for and provides the steps of,bidirectionally transferring messages among IP nodes of the IP network.Bidirectional transfer preferably takes place using TCP/IP.

FIGS. 19 and 20 are flowcharts and FIGS. 21-24 are block diagramsillustrating exemplary hardware and software for bidirectionalcommunication of SS7 user part messages between an STP and at least oneof the other SPs of an SS7 network according to embodiments of thepresent invention. The present invention can be embodied as methods,systems (apparatus), and/or computer program products. Accordingly, thepresent invention can take the form of an entirely hardware embodiment,an entirely software embodiment or an embodiment combining software andhardware aspects.

It will also be understood that one or more of the blocks in FIGS.19-24, and combinations of these blocks, can be implemented by computerprogram instructions. These computer program instructions can beprovided to a processor or other programmable data processing apparatusto produce a machine, such that the instructions which execute on theprocessor or other programmable data processing apparatus create meansfor implementing the functions specified in the flowchart block orblocks. These computer program instructions can also be stored in acomputer-readable medium that can direct a processor or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablemedium produce an article of manufacture including instruction meanswhich implement the functions specified in the flowchart block orblocks.

Accordingly, blocks in FIGS. 19-24 support combinations of means forperforming the specified functions, combinations of steps for performingthe specified functions and program instruction means for performing thespecified functions. It will also be understood that each block, andcombinations of blocks, can be implemented by special purposehardware-based computer systems which perform the specified functions orsteps, or by combinations of special purpose hardware and computerinstructions.

FIG. 19 illustrates exemplary steps that can be performed by an SS7/IPuser part message communicator embodied in an STP in processing an SS7user part message for transmission over an IP network according to anembodiment of the present invention. In step ST1 the SS7/IP user partmessage communicator receives an SS7 user part message from an SS7 node.The SS7 user part message includes an SS7 MTP level and an SS7 user partlevel, such as an ISUP level. A portion of the MTP level information canbe stripped or removed from the SS7 message, as shown in step ST2.However, according to a preferred embodiment of the invention, MTP level3 routing information is preferably retained in the message.

In step ST3, the remaining MTP level information and user part level inthe SS7 message are placed in a TCP transport layer to create a TCPmessage. The TCP transport layer preferably includes the TCP port onwhich a connection has been established with the destination SS7 or IPnode. It should be noted at this point that all of the informationcontained in the original SS7 MTP level can be placed in the TCPtransport layer, if desired. Furthermore, the MTP level information thatis ultimately included in the TCP transport layer can be modified oraltered from its original form prior to TCP encapsulation. That is, thebit stream representing the MTP level information in the original SS7MSU and the bit stream representing the MTP level information in theTCP-encapsulated message need not be identical. In addition, additionaldata, such as application-level sequence number data and operation codedata can be added to the message before or after the message is TCP- orIP-encapsulated.

In step ST4, an IP network layer is added to the TCP message to create aTCP/IP message. The IP network layer includes the destination IP addressof the node to which the original SS7 messages was addressed. Thedestination IP address can be determined using a lookup table or otherrouting mechanism based on the destination point code in the originalSS7 message. In an alternative embodiment of the invention, steps ST3and ST4 can be combined so that the TCP and IP information is added in asingle step. Finally, in step ST5, the TCP/IP message is transmitted tothe IP address over an IP network 1530 (FIG. 15) using TCP transport.The IP address can represent an SS7 node configured to communicate usingTCP/IP or a TCP/IP node without SS7 capabilities. Thus, the user partmessage can be sent from an STP, another SS7 node, or an IP node using aTCP/IP network.

FIG. 20 illustrates processing that can be performed by SS7/IP user partmessage communicator 1520 of STP 1510 (FIG. 15) in processing anIP-encapsulated SS7 message according to an embodiment of the presentinvention. As shown in step ST1, a TCP/IP message including anencapsulated SS7 user part message is received from an IP network. TheTCP/IP message includes SS7 MTP level information and user part payloaddata that are encapsulated in TCP transport and IP network layers. Instep ST2, the IP network layer is removed from the IP message to createa TCP message that includes SS7 MTP level information and SS7 user partpayload data in a TCP transport layer. In step ST3, the TCP transportlayer is removed from the TCP message to create an SS7 message includingSS7 MTP level 3 information and an SS7 user part payload level. In analternative embodiment of the invention, steps ST2 and ST3 can becombined such that the TCP/IP information is removed in one step.Additional information, such as an application-level sequence number andan operations code can be also removed from the message and processed.In step ST4, MTP levels 1 and 2 information is attached to the message,as required, to form a functional SS7 message. If no MTP levelinformation was removed from the TCP/IP message by SP 1540, then noadditional MPT levels 1 and 2 information needs to be added. Finally, instep ST5, the SS7 message is routed. Thus, message can be sent from SP1540 to STP 1510 using the TCP/IP network 1530, rather than an SS7 link.

Although the flow charts in FIGS. 19 and 20 respectively show theaddition and removal of TCP transport layer information from an SS7 userpart message, the present invention is not limited to such anembodiment. For example, in an alternative embodiment, and SS7 user partmessage can be encapsulated in a UDP/IP message for transmission over aUDP/IP network. Similarly, UDP/IP-encapsulated SS7 user part messagescan be received over a UDP/IP network and the UDP/IP portion of themessages can be removed to produce the SS7 user part messages.

Hardware for Performing Bi-Directional SS7/IP User Part MessageCommunications

FIG. 21 is a block diagram of a hardware configuration for STP 1510 thatincludes an integrated SS7/IP user part message communicator accordingto an embodiment of the present invention. As shown in FIG. 21, STP 1510includes three cooperating subsystems: maintenance and administrationsubsystem (MAS) 2102, a communication subsystem comprising a pair ofcounter rotating interprocessor message transport (IMT) buses 2104, andat least one application subsystem 2106. Application subsystem 2106 caninclude a plurality of modules. For example, at least one applicationservice module (ASM) 2108 is used to store translation tables andscreening data for gateway screening. At least one translation servicemodule (TSM) 2110 that is used for global title translation can beincluded. At least one application communication module (ACM) 2112provides unidirectional access to a remote host for STP-LANfunctionality. At least one link interface module (LIM) 2113 provides aphysical input/output terminal for two SS7 links. Each of the elements2108-2113 in application subsystem 2106 can include one or more printedcircuit cards including processing circuitry and memory devicesconfigured to perform the described functions.

According to an embodiment of the present invention, at least one datacommunications module (DCM) 2114 provides the necessary hardware forbidirectional communication of SS7 messages over an IP network. DCM 2114can include a general purpose microprocessor, network communicationshardware, program memory, and data memory for bidirectionallycommunicating SS7 user part messages over an IP network. The SS7/IP userpart message communicator 1520 (not shown in FIG. 21) can reside in theprogram memory of DCM 2114 and cause the processor to performbidirectional SS7/IP user part communications functions, as will bedescribed in more detail below. DCM 2114 performs bidirectional SS7 toTCP/IP or UDP/IP protocol stack mapping, as previously described. Asshown in FIG. 21, each DCM 2114 interfaces with both IMT bus 2104 and anassociated TCP/IP network 2116. By interfacing with IMT bus 2104, highspeed communications can be obtained with other modules in the STP 1510.

SS7/IP User Part Message Communicator

FIG. 22 is a detailed block diagram illustrating software executing onthe STP 1510 for performing bidirectional SS7/IP user part messagecommunications according to the present invention. In the illustratedembodiment, STP 1510 includes an SS7/IP user part message communicator1520. SS7/IP user part message communicator 1520 includes applicationlayer 2200 and SS7/IP converter 2201. The functions of application layer2200 and SS7/IP converter 2201 will be discussed in detail below. Thesoftware executing on LIMs 2113 a and 2113 b and DCM 2114 performscombinations of SS7 functions including message handling discrimination(HMDC) functions, message handling distribution (HMDT) functions,message handling congestion (HMGC) functions and message handlingrouting (HMRT) functions. As stated above, HMDC functions 2202 a and2202 c determine if received MSUs are destined for the STP itself andshould be processed at the STP or if the MSUs should be routed throughthe STP to another SS7 node. HMRT functions 2204 a and 2204 c determinethe signaling link over which the outgoing message is sent. HMGCfunction 2205 monitors signaling point processing load. Congestionprocedures exist to detect when the processing load is too high andperform load shedding to reduce the processing load.

Still referring to FIG. 22, when an incoming SS7 user part message 2203arrives at LIM 2113 a, the SS7 levels 1 and 2 information can be removedand the message is queued in queue 2200 a. HMDC function 2202 adetermines whether routing is required. Determining whether routing isrequired can include examining the DPC in the message. If HMDC function2202 a determines that routing is required, HMRT 2204 a routes themessage to DCM 2114 using the IMT bus 2104. Application layer 2200determines the data components that are passed on to SS7/IP converter2201. In one embodiment, application layer 2200 might determine that allof the MTP and user part payload data are to be passed onto SS7/IPconverter 2201. It should be appreciated that in alternateconfigurations, application layer 2200 can determine that only certaincomponents of the MTP layer data are needed, and consequently only aportion of the MTP level data would be passed, along with the user partpayload, to SS7/IP converter 2201. However, as will be discussed in moredetail below, application layer 2200 preferably retains the routinginformation in the SS7 user part message. In any event, the SS7/IPconverter 2201 places the MTP level information and the user part levelpayload in a TCP or UDP transport layer and adds an IP network layerincluding an IP address. Additional information, such asapplication-level sequence numbers and operation codes can also be addedto the message. TCP/IP- or UDP/IP-encapsulated message 2210 is thenrouted to the target SSP via the IP network.

Still continuing with the description of FIG. 22, an incoming TCP/IP- orUDP/IP-encapsulated user part message 2212 is received from an SP via anIP network. The SS7/IP converter 2201 removes the IP network layer andthe TCP or UDP transport layer, while any missing MTP layer informationis added so as to create a complete SS7 message including an MTP leveland a user part level. The message is queued in a queue 2200 c andprocessed by HMDC function 2202 c to determine whether routing isrequired. If routing is required, HMRT function 2204 c forwards themessage to HMGC function 2205 on LIM 2113 b. HMCG function 2205 storesthe message in a queue 2200 b. Once the message reaches the head of thequeue, outgoing unencapsulated SS7 user part message 2213 is sent to theintended SP via an SS7 link.

FIG. 23 is a block diagram illustrating message flow through STP 1510when processing user part messages sent to and received from SSP 1730over TCP/IP network 1740 according to an embodiment of the presentinvention. In FIG. 23, an SS7-formatted user part message (M1) isreceived by STP 1510 via a conventional SS7 LIM 2113. For the purposesof illustration, it is assumed that the user part message M1 is aninitial address message (IAM). Based on information contained in therouting label of the user part message M1, LIM 2113 determines that theIAM message is destined for an SSP 1730 to which STP 1510 is connectedvia TCP/IP network 1740. LIM 2113 then routes the message M1 internallyvia IMT bus 2104 to DCM module 2114. DCM module 2114 performstranslation and converts SS7 user part message M1 into a TCP/IP packet2300, wherein some or all of the MTP level 2-3 information and the userpart payload layer are transmitted, as described above. TCP/IP packet2300 is then sent across the TCP/IP network to SSP 1730.

In a second scenario, SSP 1730 generates a TCP/IP packet 2302 containingan SS7 user part message that is routed back to STP 1510. In this case,for the purposes of illustration, it is assumed that the second userpart message is an address complete message (ACM). It is also assumed inthis example that SSP 1730 generates and transmits the message in TCP/IPpacket 2302, which is similar in structure to TCP/IP packet 2300,described above. TCP/IP packet 2302 is passed through TCP/IP network1740, and eventually received by STP 1510 via the DCM module 2114.TCP/IP packet 2302 is then translated into an SS7 format by DCM 2114 androuted internally over IMT bus 2104 to the appropriate LIM module 2113and out onto the SS7 network as a user part message M2.

OAM 2304 provides operating, administration and maintenancefunctionality. This functionality includes user I/O, disk services,database updates to active cards and the general ability to load theresident software on the LIMs, ASMs, etc. HSL 2306 is a high speedsignaling link implemented according to the Bellcore GR-2878-corespecification. This high speed link is an SS7 link that operates on ATMover T1 as opposed to MTP over DSO physical network. The following tableillustrates OSI standard layers and compares MTP Low Speed Links, MTPHigh Speed Links, traditional IP and operation of a DCM according to anembodiment of the present invention. TABLE 1 Comparison of OSI Layers,MTP Low and High Speed Links, IP Layers, and DCM Functionality OSI MTPLow MTP High IP (Standard) Speed Links Speed Links (Traditional) DCMApplication ISUP ISUP — ISUP Presentation — — — — Session — — — —Transport — — TCP — Network MTP 3 MTP 3 IP MTP 3 Data link MTP-2 SAALMAC Gateway AAL-5 Adaptation Layer TCP IP MAC Physical DSO T1 10/100base-t 10/100 base-t

Data Structures

FIG. 24 illustrates a data structure for bidirectionally communicatingSS7 user part messages in internet protocol packets according to anembodiment of the present invention. In FIG. 24, SS7 MSU generallydesignated 2400 is encapsulated in transport adapter layer interface(TALI) packet generally designated 2402, which is in turn encapsulatedin IP packet 2404. More particularly, the layer 3 information in SS7 MSU2400, including the message type field, the circuit information codefield, the routing label, and the service information octet areencapsulated in service field 2406 of TALI packet 2402. The user partfield is also encapsulated in service field 2406. The remaining portionsof the SS7 MSU are preferably discarded. TALI packet 2402, in additionto the SS7 layer 3 information, includes length field 2408, opcode field2410, and synchronization field 2412. Length field 2408 specifies thelength of the data in service field 2406 of TALI packet 2402. Opcodefield 2410 specifies an SS7 message type. In this example, the opcodefield would specify an SS7 user part message type such as ISUP, TUP, orBISUP. Sync field 2412 indicates the start of a packet. Sync field 2412is useful in determining packet boundaries in TCP streams if the valuein the length field 2408 is incorrect.

TALI packet 2402 is encapsulated in data field 2414 of IP packet 2404.TCP header field 2416 includes TCP header information, such as TCP portnumbers, for bidirectional user part message communication. IP headerfield 2418 includes IP header information such as source and destinationIP addresses, for IP packet 2404. Finally, MAC header field 2420includes physical and network information for delivering the IP packet2404 over a physical network.

FIG. 25 illustrates an alternative data structure for encapsulating anSS7 user part message in an IP packet according to an embodiment of thepresent invention. The data structure illustrated in FIG. 25 providesincreased reliability using message sequencing and retrieval. In FIG.25, SS7 MSU 2400 is the same as the SS7 MSU illustrated in FIG. 24. TALIpacket generally designated 2402 a however, is different from TALIpacket 2402 illustrated in FIG. 24. In particular, TALI packet 2402 aincludes an application-level sequence number field 2500 for sequencingIP packets between SS7 nodes. In the illustrated embodiment,application-level sequence number field 2500 is included as a trailer toTALI packet 2402 a. In an alternative embodiment, application-levelsequence number field 2500 can be included as a header to TALI packet2402 a or at any other location in TALI packet 2402 a. Application-levelsequence number field 2500 provides a sequence number of a TALI packetin a communication between SS7 nodes. Processing the sequence numbervalue to provide increased reliability will be discussed in more detailbelow.

IP packet 2404 a includes data field 2414 a that includes TALI packet2402 a. Data field 2414 a thus includes application-level sequencenumber field 2500. The remaining fields in IP packet 2404 a are the sameas those illustrated in FIG. 24 and need not be further described.

FIG. 26 illustrates an exemplary SS7 message recovery routine forreliable communication of IP-encapsulated SS7 messages between SS7nodes. The SS7 message recovery routine can be software executed by SS7communication hardware in SS7 nodes. For example, the SS7 messagerecovery routine can be executed by a DCM or its equivalent in an STP.Alternatively, the SS7 message recovery routine can be executed by othernodes, such as SSPs, SCPs, or non-SS7 IP nodes for reliable IPcommunications. In FIG. 26, the SS7 packet recovery routine is explainedgenerally in terms of steps performed by two SS7 nodes. The nodes arereferred to as node A and node B, respectively. It will be understood bythose of ordinary skill in the art that either node could be an STP, anSSP, an SCP or other node.

In step ST1, node A establishes first and second TCP connections onfirst and second TCP sockets with node B. In step ST2, node A transmitsTCP/IP-encapsulated SS7 messages including application-level sequencenumbers indicating the sequence of the packets on the first socket tonode B. In step ST3, node A determines whether a socket failure hasoccurred. If a socket failure has not occurred, node A continues totransmit TCP packets to node B on socket number 1. Since TCPcommunications are bidirectional, node B can also transmit TCP packetsto node A on socket number 1. The packets transmitted from node B tonode A preferably also include application-level sequence numbersindicating the order of packets transmitted from node B to node A.

In step ST4, if a socket failure has occurred, for example on socketnumber 1, nodes A and B exchange application-level sequence numbers overthe good socket for the last packets transmitted and received. Forexample, node A transmits the application-level sequence number of thelast packet received from node B to node B. Node B transmits theapplication-level sequence number of the last packet transmitted to nodeA. Similarly, node B transmits the application-level sequence numberindicating the last packet received from node A to node A. Node Btransmits the application-level sequence number indicating the lastpacket transmitted to node A. In step ST5, node A and node B resume datacommunications on the good socket, i.e., socket 2 based on theapplication-level sequence numbers. For example, node B can transmitlost packets to node A, and node A can transmit the lost packets to nodeB on the second socket. In this manner, reliable communications areestablished between SS7 nodes even when a socket fails. Conventional TCPsequence numbering does not address this issue because TCP does notprovide a mechanism for packet retrieval when a socket fails. Theapplication-level sequence numbering of the present invention allowscommunications to resume at the point where communications were lost,rather than requiring retransmission of an entire sequence of packets.

Although the invention has thus far been described in detail withrespect to replacing SS7 links between an STP and other SS7 type SPnetwork elements with TCP/IP links, the present invention can also beemployed to facilitate communication between SS7 network elements and IPbased network elements via TCP/IP links. Furthermore, the discussion andexamples provided above specifically relate the use of the presentinvention to SS7 user part messages. However, it will be appreciated bythose skilled in the art that any SS7 message type that requires MTProuting label information in order to effectively perform or serve itsproper function can be communicated bidirectionally between SS7 and IPnetworks using the STP of the present invention.

It will be understood that various details of the invention can bechanged without departing from the scope of the invention. Furthermore,the foregoing description is for the purpose of illustration only, andnot for the purpose of limitation—the invention being defined by theclaims.

1. A method for processing an internet protocol (IP) encapsulatedsignaling system seven (SS7) user part message utilizing a signaltransfer point (STP), the method comprising: at a first STP: (a)receiving an IP-encapsulated SS7 user part message transmitted from afirst SS7 signaling point over a bi-directional IP signaling link; (b)removing an IP header from the message; (c) reading at least messagetransfer part (MTP) layer 3 information from the message; and (d)routing the message from the bi-directional IP signaling link to abi-directional SS7 signaling link based on at least the MTP layer 3information.
 2. The method of claim 1 comprising removing a transmissioncontrol protocol (TCP) header from the message.
 3. The method of claim 1comprising removing a user datagram protocol (UDP) header from themessage.
 4. The method of claim 1 wherein reading at least MTP layer 3information includes reading a destination point code (DPC) from themessage and wherein routing the message includes routing the messagebased on the DPC.
 5. The method of claim 1 comprising removing atransport adapter layer interface header from the message.
 6. The methodof claim 1 wherein receiving an IP-encapsulated user part messagetransmitted from a first SS7 signaling point over a bi-directional IPsignaling link comprises receiving an IP-encapsulated user part messagefrom a local service switching point (SSP), and the IP signaling linkthereby functions as an SS7 A link.
 7. The method of claim 1 whereinreceiving an IP-encapsulated user part message transmitted from a firstSS7 signaling point over a bi-directional IP signaling link comprisesreceiving an IP-encapsulated user part message from a second STP of thesame hierarchical level as the first STP, and the IP signaling linkthereby functions as an SS7 B link between the first and second STPs. 8.The method of claim 1 wherein receiving an IP-encapsulated user partmessage transmitted from a first SS7 signaling point over abi-directional IP signaling link comprises receiving an IP-encapsulateduser part message from a second STP, the first and second STPscomprising a mated pair of STPs, and the IP signaling link therebyfunctions as an SS7 C link between the first and second STPs.
 9. Themethod of claim 1 wherein receiving an IP-encapsulated user part messagetransmitted from a first SS7 signaling point over an IP signaling linkcomprises receiving an IP-encapsulated user part message from a secondSTP of a different hierarchical level than the first STP, and the IPsignaling link thereby functions as an SS7 D link between the first andsecond STPs.
 10. The method of claim 1 wherein receiving anIP-encapsulated user part message transmitted from a first SS7 signalingpoint comprises receiving an IP-encapsulated user part message from aservice switching point (SSP) located in a different local area from thefirst STP, and the IP signaling link thereby functions as an SS7 E linkbetween the first STP and the SSP.
 11. A computer program productcomprising computer-executable instructions embodied in acomputer-readable medium for performing steps comprising: (a) at a firstSTP: (a) receiving an internet protocol (IP) encapsulated signalingsystem seven (SS7) user part message transmitted from a first SS7signaling point over a bi-directional IP signaling link; (b) removing anIP header from the message; (c) reading at least message transfer part(MTP) layer 3 information from the message; and (d) routing the messagefrom the bi-directional IP signaling link to a bi-directional SS7signaling link based on at least the MTP layer 3 information.
 12. Thecomputer program product of claim 11 comprising removing a transmissioncontrol protocol (TCP) header from the message.
 13. The computer programproduct of claim 11 comprising removing a user datagram protocol (UDP)header from the message.
 14. The computer program product of claim 11wherein reading at least MTP layer 3 information includes reading adestination point code (DPC) from the message and wherein routing themessage includes routing the message based on the DPC.
 15. The computerprogram product of claim 11 comprising removing a transport adapterlayer interface header from the message.
 16. The computer programproduct of claim 11 wherein receiving an IP-encapsulated user partmessage transmitted from a first SS7 signaling point over an IPsignaling link comprises receiving an IP-encapsulated user part messagefrom a local service switching point (SSP), and the IP signaling linkthereby functions as an SS7 A link.
 17. The computer program product ofclaim 11 wherein receiving an IP-encapsulated user part messagetransmitted from a first SS7 signaling point over a bi-directional IPsignaling link comprises receiving an IP-encapsulated user part messagefrom a second STP of the same hierarchical level as the first STP, andthe IP signaling link thereby functions as an SS7 B link between thefirst and second STPs.
 18. The computer program product of claim 11wherein receiving an IP-encapsulated user part message transmitted froma first SS7 signaling point over a bi-directional IP signaling linkcomprises receiving an IP-encapsulated user part message from a secondSTP, the first and second STPs comprising a mated pair of STPs, and theIP signaling link thereby functions as an SS7 C link between the firstand second STPs.
 19. The computer program product of claim 11 whereinreceiving an IP-encapsulated user part message transmitted from a firstSS7 signaling point over a bi-directional IP signaling link comprisesreceiving an IP-encapsulated user part message from a second STP of adifferent hierarchical level than the first STP, and the IP signalinglink thereby functions as an SS7 D link between the first and secondSTPs.
 20. The computer program product of claim 11 wherein receiving anIP-encapsulated user part message transmitted from a first SS7 signalingpoint comprises receiving an IP-encapsulated user part message from aservice switching point (SSP) located in a different local area from thefirst STP, and the IP signaling link thereby functions as an SS7 E linkbetween the first STP and the SSP.
 21. The computer program product ofclaim 11 wherein performing steps (a)-(d) at a first STP includesperforming steps (a)-(d) at a first STP having a distributed internalprocessing architecture in which IP signaling link interfacefunctionality is separated from SS7 signaling link interfacefunctionality.
 22. The computer program product of claim 11 wherein step(a) is performed at a data communications module (DCM) within the firstSTP and wherein step (d) includes routing the message from the DCM to anSS7 link interface module (LIM) separate from the DCM and associatedwith the SS7 signaling link.
 23. The computer program product of claim11 wherein performing steps (a)-(d) at a first STP includes performingsteps (a)-(d) at a first STP having a distributed internal processingarchitecture in which IP signaling link interface functionality isseparated from SS7 signaling link interface functionality.
 24. Thecomputer program product of claim 11 wherein step (a) is performed at adata communications module (DCM) within the first STP and wherein step(d) includes routing the message from the DCM to an SS7 link interfacemodule (LIM) separate from the DCM and associated with the SS7 signalinglink.